Research peptide prices are set mainly by four things: how hard the sequence is to synthesise, how much purification it needs, whether the batch was independently tested, and how large the production run was. Two vials of the same compound at very different prices are usually not the same product.
1. Chain length and sequence difficulty
Solid-phase peptide synthesis builds a chain one residue at a time. Each coupling step has a yield below 100%, so overall yield falls geometrically with length. A tripeptide such as KPV involves a handful of steps; a 39-residue chain such as tirzepatide involves dozens, and every step adds cost and creates more opportunity for deletion sequences that then have to be removed.
Sequence content matters as much as length. Runs of proline or beta-branched residues couple poorly. Non-standard residues — D-amino acids, Aib, naphthylalanine — cost more as raw materials than the twenty standard ones. Modifications such as lipidation, PEGylation or a C-terminal amide add further steps.
2. Purification
Getting a crude peptide from roughly 70% to above 98% purity takes preparative HPLC, and it costs yield: material is discarded with the impurity fractions. The step from 95% to 99% is disproportionately expensive because the impurities that survive that far — deletion sequences differing by one residue — elute close to the main peak.
3. Testing
A batch that has been sent to an independent laboratory for HPLC and mass spectrometry carries the cost of that analysis. A batch that has not carries none. This is the single largest hidden difference between two otherwise identical listings, and it is why a published, batch-matched certificate of analysis is the thing to compare on rather than price alone. See how to read a COA and what 99% purity actually means.
4. Batch size, filling and packaging
Lyophilization, vial filling, stoppering and sealing are fixed-cost operations spread across a run. Small runs carry more overhead per vial. Proper sealed vials, correct labelling with a lot number, and packaging that survives international transit all cost more than the minimum.
Why a quoted milligram figure can mislead
Price per milligram looks like an objective comparison and often is not, because the number on the label is gross powder mass, not peptide mass. A vial at 70% net peptide content and one at 88% are not the same purchase even at the same price and the same stated weight. The arithmetic is in net peptide content vs gross weight.
What a low price usually means
- No independent testing. The most common way to be cheaper, and the hardest to detect without documentation.
- A recycled COA. A document from a different batch than the one shipped.
- Lower purity accepted. 95% and 99% are very different production costs.
- Unstated salt form or content. More counter-ion and water, less peptide, same label.
None of these are visible in a price comparison. They are visible in the batch document, which is why it should be on the product page before you buy — the full checklist is in where to buy research peptides online.
What HolyPeps charges for
Prices across the catalog reflect lyophilized material at 99%+ purity in sealed vials, with third-party HPLC and MS documentation published on each product page. Shipping is worldwide via DHL and free on orders over $150. Bacteriostatic water for reconstitution is priced separately rather than bundled into the compound price.
All products are intended for laboratory and research use only. They are not medicines, are not for human or veterinary use, and are not for diagnostic or therapeutic application.